From the German patent DE-PS No. 30 05 547, a safety mechanism is known including a safety valve which has two directional control valves placed in parallel and controlled by associated pilot valves. Each directional control valve is mechanically linked to a slide gate and connected to a supply inlet for the pressure medium via the slide gate of the other control valve. The pressure medium is supplied to one side of the consumer via a respective connection to which the directional control valves are linked.
Such a safety valve is used in a consumer which e.g. consists of a cylinder in which a piston reciprocates and in which the pressure medium is admitted at one side to move the piston from its idle position to its working position. Return of the consumer in its idle position is provided by a spring which acts on the piston.